Generally, wastewater is aerated in organic wastewater treatment using microorganisms. If the wastewater is aerated, the amount of dissolved oxygen of the wastewater is increased to activate aerobic microorganisms and further to accelerate the removal of suspended materials and harmful gas, thus raising wastewater treatment efficiencies. Even the water in a tank of a fish farm is aerated, and in this case, an amount of dissolved oxygen is increased to prevent the water from being contaminated and further to help the growth of live fish. Further, the aeration prevents water bloom and red tide from occurring.
A conventional aeration device is disclosed in Korean Patent Registration No 1254873 (Apr. 9, 2013). FIG. 1 is a sectional view showing the conventional aeration device. As shown in FIG. 1, the conventional aeration device includes a hollow cylindrical casing 100, a mixing unit 200 formed in front of the casing 100, an impeller 300 located inside the mixing unit 200, a separator plate 400 located on the front side of the mixing unit 200, an intake housing 500 located in front of the separator plate 400, an air inflow unit 600 located to pass through the intake housing 500 and serving as an air inflow passage, and a discharge unit 700 located on the outer peripheral surface of the mixing unit 200.
The casing 100 has a motor 130 sealedly mounted therein, and a driving shaft 135 of the motor 130 protrudes forward. Further, the casing 100 has an openable cover 120 coupled to the rear side thereof, and the cover 120 is provided with a handle 150 and an electric wire 140 for supplying driving power to the motor 130.
The mixing unit 200 has a shape of a hollow cylinder open forward and includes a discharge hole 230 penetrated radially into the circumferential surface thereof. The driving shaft 135 of the motor 130 is extended forward from the rear of the mixing unit 200. The driving shaft 135 is rotatably supported against a bearing member 170 located inside the casing 100, and a sealing member 190 is located between the driving shaft 135 and the inner periphery of the mixing unit 200 at the front side of the bearing member 170.
The impeller 300 is coupled to the driving shaft 135 to generate a thrust force in the radial direction of the mixing unit 200 and includes a disc-shaped rotary plate 310, a support tap 330 having an insertion hole adapted to insert the driving shaft 135 thereinto, and a plurality of rotary wings 320 protruding forward from the rotary plate 310. The support tap 330 protrudes forward to form a gap in the radial direction between the inside end portions of the rotary wings 320 and the support tap 330. The impeller 300 is rotated unitarily with the driving shaft 135 of the motor 130 through the driving of the motor 130.
The separator plate 400 has a disc-shaped plate having an inflow hole 410 formed on the center portion thereof in such a manner as to be penetrated from the front to the rear. The intake housing 500 has a shape of a cylinder open on the rear side thereof and includes a plurality of intake holes 510 formed penetratedly in the radial direction on the cylindrical portion thereof in such a manner as to be spaced apart from each other along the circumferential direction thereof. The separator plate 400 is located between the intake housing 500 and the mixing unit 200.
The air inflow unit 600 is penetrated from the front of the intake housing 500 to the rear thereof and includes a hollow inflow tap 610 open on one side and the other side thereof, a hollow inflow pipe 630 connected to the front side of the inflow tap 610 in such a manner as to be open on one side and the other side thereof, and a hollow extension pipe 650 connected to the rear side of the inflow tap 610 in such a manner as to be extended toward the mixing unit 200. A gap ‘t’ is formed in the longitudinal direction between the rear side end portion of the extension pipe 650 and the support tap 330. The inflow tap 610 has a bent structure.
The discharge unit 700 includes a hollow discharge tap 710 open on one side and the other side thereof in such a manner as to communicate with the discharge hole 230 and a hollow discharge pipe 730 open on one side and the other side thereof in such a manner as to be connected to the discharge tap 710. The discharge pipe 730 includes a large diameter portion 731 formed on the front portion thereof and a small diameter portion 735 formed on the rear portion thereof.
According to the conventional aeration device, water is filled in the inflow pipe 630 to the same height as the surface of water before the aeration device is driven, and if the motor 130 is rotated at the initial driving of the aeration device, the water filled in the inflow pipe 630 is all introduced. After that, air is introduced and mixed with the water passing through the intake holes 510.
If the conventional aeration device is installed at a relatively low depth from the surface of water, for example, if the air inflow unit 600 is submerged into water to a depth of 30 cm, the water filled in the inflow pipe 630 is sucked by the driving force of the motor 130 so that air is introduced through the air inflow unit 600. Contrarily, if the air inflow unit 600 is submerged into water to a depth of 50 cm or more, all the water filled in the inflow pipe 630 is not sucked so that air is not introduced through the air inflow unit 600. Accordingly, the conventional aeration device cannot be used at a high depth under water. That is, air and water are mixed only on the surface of water to discharge the mixed air and water through the discharge unit 700. So as to increase the depth, therefore, the motor 130 should have high power output.